Platform lift apparatus for attic storage space

ABSTRACT

A platform lift apparatus enables the safe movement of objects to and from an attic storage space. The platform lift apparatus includes a frame, a drive mechanism, and a platform. The frame includes internal and external mounting surfaces. The drive mechanism is substantially disposed within the frame and is coupled to the internal mounting surfaces. The drive mechanism includes a plurality of rotatable, parallel shafts with each shaft further including at least one lift drum having an associated lift tether at least partially wound thereon and having an end hanging therefrom. The platform is coupled to each lift tether end and is thereby suspended from the frame. The platform is selectively movable by operation of the drive mechanism within in a vertical dimension between raised and lowered positions. The drive mechanism further comprises an electric motor operatively coupled to the plurality of parallel shafts.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to residential or commercial storage, or more particularly, to a platform lift apparatus for raising or lowering objects relative to an upper storage location such as an attic storage space located above a garage or living quarters.

2. Description of Related Art

Many homes have attic spaces above garages and living quarters, and these attic spaces often provide a storage location for various items. While some attic spaces are finished and have access via a stairwell, most attic spaces remain unfinished and have more rudimentary access systems. The most basic access system is a simple opening or scuttle hole formed in the ceiling dividing the attic space from the room below. The scuttle hole is commonly located in a closet or main hallway, and may be covered by a hatch that comprises a removable portion of ceiling, such as formed from plywood or drywall. A user would position a ladder below the opening and access the storage space by carrying storage objects up and down the ladder. An improvement over this basic access system is a pull-down ladder that is built into a hingedly attached door covering the opening. The pull-down ladder may be folded into a plurality of sections to provide a compact structure when stowed. The user opens the door and unfolds the ladder to bring it into an operational position. This pull-down ladder has improved convenience since the user does not have to transport a ladder to and from the access location, and the ladder is anchored to the opening to thereby provide an increased degree of safety for the user.

Nevertheless, a drawback of each of these access systems is that it is difficult to transport objects up and down the ladder. The user cannot easily carry the object and grasp the ladder at the same time, thereby forcing a dangerous tradeoff between carrying capacity and safety. Moreover, the size and weight of the objects that may be transported is limited to that which could be manually carried and fit through the dimensions of the access opening. Users of such access systems have a substantial risk of injury due to falling and/or dropping objects, and the objects themselves can be damaged as well.

Thus, it would be advantageous to provide an improved way to transport objects to and from an attic storage space without the drawbacks and safety risks of the known access systems. Additionally, there are many other applications in which it would be desirable to transport objects to and from a raised position.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the platform lift system will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings, which will first be described briefly.

FIG. 1 is an isometric view of a platform lift system in accordance with an embodiment of the invention;

FIG. 2 is a top view of the platform lift system and associated platform;

FIG. 3 is a sectional view of the platform lift system as taken through the section C-C of FIG. 2;

FIG. 4 is a sectional view of the platform lift system as taken through the section A-A of FIG. 2;

FIG. 5 is a sectional view of the platform lift system as taken through the section B-B of FIG. 2;

FIG. 6 is a side view of a lift pulley having a belt tensioner;

FIG. 7 is a front view of the lift pulley of FIG. 6;

FIG. 8 is a top view of an embodiment of a platform including an integrated basket;

FIG. 9 is a side view of the platform of FIG. 8;

FIG. 10 is a rear view of the platform of FIG. 8;

FIG. 11 is a side view of an alternative embodiment of a platform lift system that does not include a ceiling opening;

FIG. 12 is a front view of a drop down storage system in accordance with another embodiment of the invention;

FIG. 13 is a sectional view of the drop down storage system as taken through the section D-D of FIG. 12;

FIG. 14 is a top view of an alternative embodiment of the platform lift system that includes an integrated ladder;

FIG. 15 is a side view of the platform lift system of FIG. 14;

FIG. 16 is a front view of the platform lift system of FIG. 14;

FIG. 17 is a top view of another embodiment of the platform lift system that includes a pull-down ladder;

FIG. 18 is a side view of the platform lift system of FIG. 17;

FIG. 19 is an end view of the platform lift system of FIG. 17;

FIG. 20 is a cross-sectional side view of another embodiment of the platform lift system that includes a pull-down ladder;

FIG. 21 is a cross-sectional side view of the platform lift system of FIG. 20;

FIG. 22 is a top view of the platform lift system of FIG. 20;

FIG. 23 is a top view of the platform lift having traversed partly downward along the guide affixed to the ladder;

FIG. 24 is a side cutaway view of the platform pulley length adjust assembly;

FIG. 25 is an end view of the platform pulley length adjust assembly;

FIG. 26 is a sectional view of the reduction gears as taken through the section C-C of FIG. 22;

FIG. 27 is a side view of an embodiment of the platform lift having an impact detection system;

FIG. 28 is an enlarged side view of a portion of the impact detection system of FIG. 27;

FIGS. 29 a-c are side views of an alternative transition mechanism to permit the lift platform of FIG. 22 to transition to the ladder guide;

FIGS. 30 a-c are an alternative drive system for the platform lift system;

FIGS. 31 a-c are an another alternative drive system for the platform lift system;

FIG. 32 a-b are yet another alternative drive system for the platform lift system;

FIG. 33 is an alternative embodiment of a platform lift system adapted to move a load between interior and exterior structures;

FIG. 34 is another alternative embodiment of a platform lift system adapted to engage a window ledge;

FIG. 35 is a side view of another alternative embodiment of a platform lift system movable along a monorail;

FIG. 36 is a front view of the platform lift system of FIG. 35;

FIG. 37 is a perspective view of another alternative embodiment of a platform lift system having an expandable frame assembly;

FIG. 38 is a side view of another alternative embodiment of a platform lift system used in connection with an overhead rail;

FIG. 39 is a front view of another alternative embodiment of a lift system used to raise an enclosed compartment;

FIG. 40 is a top view of the lift system of FIG. 39; and

FIG. 41 is a side view of the lift system of FIG. 39.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention satisfies the need for an improved way to transport objects to and from an attic storage space without the drawbacks and safety risks of the known access systems. In the detailed description that follows, like element numerals are used to describe like elements illustrated in one or more figures.

More particularly, the invention provides a platform lift system that enables objects to be moved between an attic space and a room below. The platform lift system includes a frame that is mounted into a scuttle hole formed in an attic ceiling and a platform that is supported by the frame. The platform may be selectively raised or lowered in order to transport objects to/from the attic space. When in a raised position, the platform engages the frame and seals the attic space to provide a thermal barrier. The frame lies substantially flush with the ceiling floor, so as to maximize available storage space within the attic ceiling and minimize interference between the lift system and objects moved on and off the platform. The frame further includes a drive system that controls the movement of a plurality of belts that are coupled to the platform. The platform is raised by withdrawing the belts, and is lowered by paying out the belts.

Referring first to FIG. 1, an isometric view of a platform lift system is illustrated in accordance with an embodiment of the invention. The platform lift system is installed in a ceiling structure that is supported by horizontally extending joists 21. A rectangular scuttle hole is formed within the ceiling structure that is bounded on two sides by joists 21 and on the other sides by crosspieces that abut the joists. As shown in FIG. 1, a section of an intermediary joist is removed for the length of the scuttle hole, such that the width of the scuttle hole corresponds to twice the separation between adjacent joists plus the width of one joist. As will be understood to persons skilled in the art, the platform lift system maintains the structural integrity of the ceiling notwithstanding the removal of a section of joist.

The platform lift system further comprises a vertically oriented frame 11 having a rectangular shape adapted to fit into the scuttle hole formed in the ceiling. The frame 11 may include mounting brackets 12 or integral flanges (not shown) that engage upper surfaces of the joists and crosspieces to facilitate attachment thereto. The frame 11 may be constructed of wood, metal, plastic, or other high strength, lightweight material capable of supporting a suitable load carried by the platform lift system.

A drive system coupled to the frame raises and lowers a platform (described below). In an embodiment of the invention, the drive system includes shafts 31, 32, shaft drive gear 34, motor 41, motor drive gear 46, belt drive gears 51, and drive belts 56. The shafts 31, 32 are rotatably mounted in parallel at opposite ends of the frame 11. Each end of the shafts 31, 32 includes a belt drive gear 51 mounted thereto in substantial alignment. This way, the respective belt drive gears on the left end of the shafts 31, 32 are aligned and the respective belt drive gears on the right end of the shafts are similarly aligned. The left and right belt drive gears 51 carry respective right and left drive belts 56. Shaft 31 further carries shaft drive gear 34. Motor 41 is mounted to the frame 11 using suitable brackets and is adapted to drive motor drive gear 46, which is in turn arranged in mesh with the shaft drive gear 34. Accordingly, motor 41 drives shaft 31 to rotation by cooperation of the motor drive gear 46 and shaft drive gear 34, and shaft 32 is driven to rotation in unison with shaft 31 by cooperation of the belt drive gears 51 and drive belts 56. In a preferred embodiment of the invention, the shafts 31, 32 are keyed to match associated keying of the belt drive gears 51 and shaft drive gear 34 so as to maintain synchronized movement of the shafts. Further, the drive belts 56 may include teeth that engage associated sprockets of the belt drive gears 51 to further maintain synchronized shaft movement. Motor 41 may further include speed reduction gearing 42 and bearings 44 to achieve a desired rotational rate of the shafts 31, 32.

The shafts 31, 32 further carry a plurality of pulleys 52 for raising and lowering lift belts 55. Each shaft has lift pulleys 52 disposed at both ends such that one pulley is located adjacent to each corner of the frame 11. The lift pulleys 52 carry a respective lift belt 55 that winds onto the pulley. A first end of each lift belt 55 is fixedly attached to a respective lift pulley 52, and a second end of the lift belt 55 hangs vertically from the pulley and is attached to the platform (described below). With respect to shaft 32, the drive system further includes idler pulleys 57 that serve to move the respective lift belts toward the outer periphery adjacent to the frame 11. It should therefore be understood that when motor 41 is driven to rotation in a clockwise direction, shaft drive gear 34 and shafts 31 will each be driven to rotation in a counter-clockwise direction to unwind the lift belts 55 and thereby lower the platform. Conversely, when motor 41 is driven to rotation in a counter-clockwise direction, shaft drive gear 34 and shafts 31 will each be driven to rotation in a clockwise direction to rewind the lift belts 55 and thereby raise the platform. It will be appreciated that the platform lift system will include suitable control circuitry for activating the motor 41 in forward and reverse directions.

FIG. 2 illustrates a top view of the platform lift system and associated platform 60. Likewise, FIGS. 3, 4 and 5 illustrate sectional views of the platform lift system as taken through the section C-C, A-A, and B-B of FIG. 2, respectively. As best shown in FIGS. 4 and 5, the platform 60 includes a base 64 comprising a generally rectangular board having a shape corresponding to the scuttle hole. The platform 60 may further include vertically extending fences that define a carrying basket (described below). As shown in FIG. 4, the base 64 may further include a seal 65 disposed on an upper surface therefore adjacent to an outer periphery of the base so as to form a thermal barrier and also to cushion the engagement of the platform 60 with the frame 11 when the platform is in the fully raised position. The frame 11 and the base 64 may further be provided with respective guide ramps 62, 61 that facilitate the engagement of the platform 60 with the frame. FIG. 5 shows the engagement between the lift belts 55 and the platform 60. In a preferred embodiment of the invention, the ends of the lift belts 55 are provided with a fastening device 66, such as a quick release fastener, that engages a corresponding receptacle 63 coupled to the platform 60. This permits the platform 60 to be disconnected from the lift belts 55, such as to facilitate loading of objects onto the platform. It should be appreciated that a permanent connection between the platform 60 and the lift belts 55 could also be advantageously utilized.

Although the frame 11 is illustrated as a fixed rectangular shape, it should be appreciated that the frame may be adjustable to achieve different widths and/or lengths. The shafts 31, 32 may be provided with adjustable length, such as using telescoping shaft segments that are fixed in position by tightening a set screw.

FIGS. 6 and 7 illustrate an embodiment of the lift pulleys 52 having a belt tensioner. More particularly, the belt tensioner includes a tension spring 71 mounted to a portion of the frame 11. The tension spring 71 may be formed of a flexible band, such as a leaf spring. The tension spring 71 further includes a collar 70 that carries an axle 69. A tension drum 68 is rotatably coupled onto the axle 69. The tension drum 68 is biased into physical engagement with the lift belt 55 that has wound onto the lift pulley 52, such that a constant pressure is applied to the lift belt 55 as it is either played out or re-wound onto the lift pulley 52 as the platform 60 is selectively lowered or raised. It should be appreciated that each of the four lift pulleys 52 would have a like belt tensioner.

FIGS. 8, 9 and 10 illustrate an embodiment of a platform 60 that includes an integrated basket. The platform 60 further includes a plurality of folded fences 75, 76, 77 and 78. The fences are each hingedly attached to respective outer edges of a basket region, and are pivotable between horizontal and vertical positions. In the horizontal (or collapsed) position, fences 77 and 78 are nested below fences 75, 76. Each fence comprises a generally rectangular shape corresponding to roughly one-half of the area defined by the basket region. With the fences disposed in the horizontal or collapsed configuration, a flat surface is defined onto which objects may be carried. Alternatively, with the fences deployed to the vertical position, a generally rectangular basket is formed into which objects may be placed. A latching mechanism may be included that attaches the fences together in the vertical position in order to maintain the basket. It should be appreciated that the basket may be advantageous for transporting small objects that might otherwise fall off the platform while it is being raised or lowered. The platform 60 may also include a fixed position or fold-down ramp that facilitates loading of objects thereon.

FIG. 11 illustrates a side view of an alternative embodiment of a platform lift system. Unlike the preceding embodiments in which the platform carried objects through a scuttle hole formed in an attic ceiling, the embodiment of FIG. 11 carries objects to a storage location disposed below the ceiling. This embodiment might be advantageous in a garage or loft in which there is a high ceiling but no attic space above the ceiling. Objects could be carried up to this storage location, thereby clearing floor space below. The frame 11 of the platform lift system would be mounted to the ceiling, such as using angle brackets 80. In the same manner as described above in any of the foregoing embodiments, lift belts 55 would carry a platform 83. The platform 83 may have vertically extending alignment guides 81 that engage corresponding stops 82, which serve the purpose of defining the vertical extent of travel of the platform and guiding the platform into an aligned position.

FIG. 11 also illustrates a retractable wheel assembly affixed to a bottom surface of the platform 83. The wheel assembly includes a rotable wheel or caster 91 that rotates about an axle 90. The wheel assembly is shown in a retracted (or horizontal) position. By pivoting the wheel assembly 90° about a pivot point 88, the wheel assembly can be moved to an operational position with the wheel 91 oriented vertically. The retractable wheel assembly enables the platform 83 to serve as a dolly for the purpose of moving objects around the floor, after disengaging the lift belts 55. It should be appreciated that all four corners of the platform 83 may include like retractable wheel assemblies. Moreover, the retractable wheel assemblies could also be used with any of the foregoing embodiments of the invention.

FIGS. 12 and 13 illustrate yet another embodiment of the invention providing a drop down storage system. Unlike the preceding embodiments, the drop down storage system provides a storage unit 100, such as a pantry or cabinet, which can be lowered down from the ceiling to enable access. When not in use, the storage unit 100 can be raised back through the ceiling, with the bottom surface of the storage unit ending flush with the ceiling. The storage unit 100 may include a plurality of shelves or drawers or rolling pantry trays 102 (as shown in FIGS. 12 and 13). The storage unit 100 would be raised or lowered substantially as described above, except that the frame 11 is disposed above the ceiling rather than flush with the ceiling. In addition to the lift belts 55 described above, the drop down storage system may also include a scissor stabilizer assembly formed from a plurality of scissor linkages 111 coupled at pivot points 112. An uppermost linkage 114 and lowermost linkage may have ends that travel in respective tracks 114 that permit the scissor stabilizer assembly to expand and retract. The scissor stabilizer assembly provides smooth, controlled motion of the storage unit 100 as it raises and lowers.

FIGS. 14-16 illustrate yet another embodiment of the invention providing a lift platform system that includes a pull-down ladder. The pull-down ladder may be folded into a plurality of sections to provide a compact structure when stowed, and may be hingedly attached to a door that seals a scuttle hole formed in the ceiling. When in the unfolded configuration, the rails of the ladder provide a track to guide the movement of a platform. The platform includes wheels extending from one edge thereof, with the wheels adapted to engage the track provided by the ladder. The platform would be raised and lowered substantially as described above, except that rather than traveling vertically between raised and lowered positions, the platform travels diagonally along the track provided by the ladder. This embodiment is advantageous since a user would only have to provide a single scuttle hole through the ceiling to provide for human access and movement of stored objects.

More particularly, FIG. 15 illustrates fold-down ladder 125 installed in a ceiling structure that is supported by horizontally extending joists 21. The ladder 125 comprises a plurality of horizontal steps 126 and may be folded into a plurality of sections that permit the ladder to be stowed in the scuttle hole and enclosed in the ceiling when not in use. The ladder 125 is attached to an edge of the scuttle hole by a hinge 129. When the ladder 125 is fully deployed, it extends downward at an angle of roughly 45-75° and comes into contact with the floor at the bottom of the ladder. The supporting frame (not shown) for a platform lift is installed above the scuttle hole, such as supported by rafters substantially above the floor of the attic space. The platform 64 may be raised above the scuttle hole to a height sufficient to permit users to climb the ladder 125 and access the attic space without being impeded by the platform.

As shown in FIGS. 14-16, the platform 64 is suspended by lift belts 55 in the same manner as described above with respect to the preceding embodiments. The platform 64 of this embodiment further includes a pair of portal guide rollers 132 and a pair of ladder guide rollers 133 supported by roller support brackets 131 that extend substantially horizontally from an end of the platform. The portal guide rollers 132 are arranged to engage respective roller guides 130 disposed in a vertical orientation at opposite corners of an end of the scuttle hole. The ladder 125 further includes a roller guide 127 that extends the length of the ladder. Accordingly, when the platform 64 is lowered from the overhead stowed position, the portal guide rollers 132 engage the roller guides 130, which guides the platform downward in a substantially vertical direction. Then, when the guide rollers 132 reach the bottom of the roller guides 130, the ladder guide rollers 133 engage the roller guide 127 on the ladder 125. As the platform 64 descends, its direction of travel transitions from substantially vertical to the angle defined by the position of the ladder 125. The platform 64 will continue to descend along a track defined by the roller guide 127 until reaching the floor or selectively stopped by the user. A pair of guide rollers 144 may also be disposed at an end of the scuttle hole opposite the roller guides 130. The guide rollers 144 engage an end of the platform 64 as it descends through the scuttle hole.

FIGS. 17-19 illustrate another embodiment of the invention providing a lift platform system that includes a pull-down ladder. In this embodiment, the platform system moves laterally along an overhead rail system. When it is desired to use the ladder to access the attic space, the platform is moved laterally to a position out of the way of the scuttle hole. But, when it is desired to use the platform lift system, the platform is moved laterally to a position aligned with the scuttle hole. From this position, the platform can be raised and lowered diagonally along the track provided by the ladder in the same manner as described above in the preceding embodiment. More particularly, a pair of platform frame tracks 135 are coupled to the floor of the attic space with corresponding mounting assemblies 138. The platform assembly includes a plurality of sleeves 136 that engage the tracks 135, permitting horizontal movement of the entire platform assembly. The platform assembly may thereby be moved horizontally between an operational position aligned with the scuttle hole and a non-operational position moved out of the way of the scuttle hole.

FIGS. 20-22 illustrate another embodiment of the invention providing a lift platform system that includes a pull-down ladder. In this embodiment, the platform system moves laterally along a rail disposed on the floor of the attic space. As in the preceding embodiment, when it is desired to use the ladder to access the attic space, the platform is moved laterally to a position out of the way of the scuttle hole. But, when it is desired to use the platform lift system, the platform is moved laterally to a position aligned with the scuttle hole. From this position, the platform can be raised and lowered diagonally along the track provided by the ladder in the same manner as described above in the preceding embodiment.

The lift platform system includes three main subsections: (a) a joist sleeve frame structure that engages a scuttle hole formed in a ceiling; (b) an unfoldable ladder and hatch door that is hingedly attached to the joist sleeve frame structure; and (c) a movable platform carriage assembly with platform lift. All three of these subsections are shown in FIG. 20. A scuttle hole is bounded by joists 21 that form the ceiling. A joist sleeve frame 151 is inserted into and fixedly engaged with the scuttle hole so as to provide structural integrity for other subsections of the lift platform system. The sleeve frame 151 is coupled to track 159 using angle brackets 160. The track 159 lies horizontally on the floor of the ceiling to provide a guide path for the movable platform carriage assembly. A roller guide 245 extends from a side of the sleeve frame 151 via bracket 243 to guide movement of the platform through the scuttle hole. Ladder 225 is shown in an unfolded configuration extending diagonally downward from the joist sleeve frame 151. The ladder includes a roller guide 227 extending along the length thereof for engagement with a corresponding roller of the movable platform. The movable platform frame 211 is shown above the joist sleeve frame 151. The moveable platform is shown in a fully raised position 264 a and partly lowered position 264 b. As in the foregoing embodiments, the platform 264 is supported by a plurality of lift belts 55 that unwind from respective lift pulleys 52 and idler pulleys 156.

FIGS. 21 and 22 shown the moveable platform carriage assembly in greater detail. The drive mechanism for lifting the platform includes a motor 41 that drives an associated motor shaft 150, and a plurality of helical gears driving a main shaft 270 with desired speed reduction. The platform frame 211 further includes a plurality of track roller wheels 271 that permit lateral movement of the platform carriage assembly along the track 159 (described above). The track roller wheels 271 are coupled to the platform frame 211 using axles 272.

In an embodiment of the invention, the lift pulleys 52 further include torsional springs 269 that couple the pulleys to the main shaft 270. The torsional springs 269 allow for differential stretch length of the lift belts 55. Since two pulleys at one end of the platform lift the platform directly, while two others guide the lift belts laterally across the width of the platform to the pulleys at the other end before dropping down to lift the platform, differential stretching of the lift belts can result in the platform being moved unevenly. The amount of this differential stretching will also depend on the amount of loading of the platform. The torsional springs 269 are selected to have a spring constant k that matches the expected stretching, and will allow relative motion of the lift pulleys 52 with respect to the shaft 270 no matter what force is applied to the platform. FIG. 21 further shows a platform pulley length adjustment mechanism 152 that enables the connection between the lift belts 55 and the platform to be adjusted. Tightening the set screw of the platform adjustment mechanism 152 serves to change the length of the lift belts. The adjustment mechanism 152 is described in greater detail below with respect to FIGS. 24 and 25.

FIG. 23 shows the platform of the preceding figures having traversed downward through the scuttle hole in the ceiling. In this embodiment, the platform includes a ladder guide bracket 154 that is coupled to the side of the platform 260 using a rotating joint 153. The guide bracket 154 carries guide rollers 232, 233 that engage the roller guide 227 affixed to the ladder.

FIGS. 24 and 25 show the pulley belt adjustment mechanism 152 in greater detail. An end of the belt 55 enters a slot 276 formed in an upper surface of the movable platform and enters an interior chamber. A threaded bolt 277 extends the length of the chamber and a slide block is threadingly coupled to the bolt. The belt 55 is affixed to the slide block. Turning the bolt 277 in a clockwise direction causes movement of the slide block within the chamber toward the head of the bolt, thereby loosening the belt 55. Conversely, turning the bolt 277 in a counter-clockwise direction causes movement of the slide block within the chamber away from the head of the bolt, thereby tightening the belt 55. It is anticipated that all four corners of the platform include a like mechanism for adjusting the belt length. The platform may also be equipped with a bubble level to enable the operator to accurately adjust the pulley belt adjustment mechanisms to level the platform. Instead of a manual adjustment, the same mechanism could be adapted to automatically level the platform each time it is operated.

FIG. 26 shows the gear train used to drive the main shaft, taken through the section C-C of FIG. 22. The motor 41 drives a helical gear 290, which is in mesh with helical gear 291 affixed to a worm shaft 292 oriented 90° to the motor shaft. The worm shaft 292 carries worm 293, which drives worm gear 294 coupled to main shaft 270. As discussed above, the main shaft 270 drives the pulleys 52 that raise and lower the lift belts 55. It is anticipated that the gear train achieve a generally high gear reduction ratio (approximately 30:1).

FIG. 28 illustrates a side view of the lift platform having an impact detection system for the platform lift system. A contact plate 301 is coupled to the underside of the platform deck 360 using a plurality of pins 302. The pins 302 are fixed to corresponding compression springs 304, which are fixedly attached at an end to the platform deck 360. The arrangement permits the contact plate 301 to be movable against the bias applied by the compression springs 304. Electrical contacts disposed within the compression springs 304 make contact when the contact plate 301 causes one or more of the pins 302 to compress the associated compression springs 304. Accordingly, if the platform deck 360 comes into contact with an object as the lift platform is descending, the signal electrical signal formed by the closed contacts could trigger a halt to the movement of the lift platform.

FIGS. 29 a-c illustrate a transition mechanism that enables the movable platform to transition from vertical movement to the diagonal movement along the ladder. FIG. 29 a shows the transition mechanism in a deployed configuration, with the ladder 225 extended downward from the pivot axle 247 that is fixed to the joist sleeve frame 151. Roller guide 227 is coupled to the ladder 225 and provides a guide path for movement of the platform lift. A folding roller track mechanism 306 includes a track segment 309 that provides a continuous path with the roller guide 227 to enable transition from vertical to diagonal movement. The track segment 309 and roller guide 227 are oriented to engage the guide roller 233 coupled to the platform via bracket 154. As shown in FIG. 29 a, the guide roller 233 first moves vertically in contact with the track segment 309. Then, upon reaching an elbow defined by the intersection of track segment 309 and roller guide 227, the guide roller 233 transitions to a diagonal path. Fence 311 keeps the guide roller 233 in contact with the track segment 309. Spring 312 biases the folding roller track mechanism 306 into position when the ladder is deployed. It should be appreciated that the fence 311 contains the guide roller 233 on the outside as the guide roller moves vertically. Following the transition to diagonal movement, the ladder 225 provides an inner fence for the guide roller 233. Accordingly, the guide roller 233 is controlled throughout its travel.

FIG. 29 b shows the transition mechanism in a stowed configuration, with the ladder 225 folded up and the attic hatch closed. The roller track mechanism 306 is moved out of the way to permit the ladder 225 to move upward as it is stowed. FIG. 29 c shows a sectional view of the roller track mechanism 306 as taken through the section A-A of FIG. 29 b. An advantage of using the folding roller track mechanism 306 of FIGS. 29 a-c is that it avoids the need for redundant sets of guide rollers on the platform.

FIGS. 30 a-c illustrate an alternative embodiment of the drive system for the platform lift system. Instead of a continuous loop, the drive belt 456 has a first end fixedly attached to the first belt drive gear 452 and a second end fixedly attached to the second belt drive gear. The drive belt 456 is wound onto the belt drive gears, such that when the platform is fully raised the drive belt is completely wound onto the first belt drive gear 452 and when the platform is fully lowered the drive belt is completely wound onto the second belt drive, gear. By fixedly attaching the ends of the drive belts 456 to the belt drive gears 452, the belt provides a limit to the amount of vertical travel of the platform. Also, the shaft 432 is offset vertically with respect to shaft 431, and the drive belt 456 is wound onto the belt drive gears in opposite directions. Thus, the first belt drive gear rotates counterclockwise while the second belt drive gear rotates clockwise, and vice versa. This arrangement has the advantage of paying out the lift belts from the outer periphery of the pulleys, thereby eliminating the need for separate idler pulleys (see FIG. 1) to manipulate the lift belt to the periphery. It should be appreciated that only the belt drive gears at one end of the shafts 431, 432 are illustrated in FIGS. 30 a-c, and that the other ends would have a like construction.

FIGS. 31 a-c illustrate another alternative embodiment of the drive system for the platform lift system. In this embodiment, two of the lift pulleys are eliminated and the belt 556 provides both driving and lifting. Particularly, the drive belt 556 has a first end fixedly attached to the first belt drive gear 552 and a second end that is carried partly by the second belt drive gear and then extends vertically to provide a lift belt. Pulley 551 provides a second lift belt in the same manner described above with respect to FIG. 1. When the platform is fully raised, the drive belt 556 is completely wound onto the first belt drive gear 552 and when the platform is fully lowered the drive belt is completely paid out. As in the preceding embodiment, the shaft 532 is offset vertically with respect to shaft 531, and the drive belt 556 causes the belt drive gears to rotate in opposite directions. Thus, the first belt drive gear rotates counterclockwise while the second belt drive gear rotates clockwise, and vice versa. This arrangement has the advantage of reducing the number of lift pulleys and associated belts. It should be appreciated that only the belt drive gears at one end of the shafts 531, 532 are illustrated in FIGS. 31 a-c, and that the other ends would have a like construction.

FIGS. 32 a-b illustrate yet another alternative embodiment of the drive system for the platform lift system. In this embodiment, all of the lift pulleys are eliminated and the belt 656 provides both driving and lifting. Particularly, the drive belt 656 has a first end fixedly attached to the first belt drive gear 652 and a second end that is carried partly by the second belt drive gear and then extends vertically to provide a lift belt. The first belt drive gear 652 also includes a separate lift belt 655 that is wound onto the drive gear along with the drive belt 656. When the platform is fully raised, the drive belt 656 and lift belt 655 are completely wound onto the first belt drive gear 652 and when the platform is fully lowered the drive belt 656 and lift belt 655 are completely paid out. As in the preceding embodiment, the shaft 632 is offset vertically with respect to shaft 631, and the drive belt 656 causes the belt drive gears to rotate in opposite directions. It should be appreciated that only the belt drive gears at one end of the shafts 631, 632 are illustrated in FIGS. 32 a-b, and that the other ends would have a like construction.

FIG. 33 is an alternative embodiment of a platform lift system adapted to move items from outside a structure to an interior raised position. For example, the platform lift system could raise a load disposed on ground level outside a building and transport the load through an upper window into an interior of the building. As shown in FIG. 33, the structure includes an exterior wall 703 and a raised room having floor 707. A modular frame assembly 702 provides vertical support for a platform lift mechanism having wheels 771 that engage track 759. The platform lift mechanism Includes platform 760 that is raised and lowered using belts that attach at lift points 766. A load 704 may be strapped to the platform using restraints 705. Pulleys 752 raise and lower the belts as substantially described above. With the load 704 and platform 760 in the raised position, the entire platform lift mechanism may be moved laterally along the track 759 to a position outside a window or balcony. The load 704 may then be lowered to the exterior floor by operation of the platform lift. The same process in reverse would be used to move a load into the structure.

FIG. 34 illustrates another alternative embodiment of a platform lift system adapted to move items from a window ledge. A frame assembly 802 is positioned in an interior space, and has foldable members that extend along an interior wall and out through a window. The frame assembly 802 supports a vertical rail 859 on which a platform lift mechanism travels. The platform lift mechanism includes wheels 871 that engage the vertical rail to permit the platform to be transferred between interior and exterior positions. As in the preceding embodiments, the platform lift mechanism includes a platform 860 that is lifted using belts coupled to pulleys 852. It is anticipated that the frame assembly 802 not be permanently installed, but rather be merely secured in place ballast. This way, the platform lift mechanism can be deployed when it is need to move an object, and can otherwise be disassembled and put away.

FIGS. 35 and 36 illustrate another alternative embodiment of a platform lift system that is movable along a monorail 901. The monorail 901 is coupled to the ceiling 958 using periodic mounting brackets 902 that are spaced along a travel path. A platform lift system includes a platform frame 911 having brackets 903 holding roller wheels 971. The monorail 902 includes a track that engages the roller wheels 971, enabling the platform frame 911 to be transported along the travel path. As in the foregoing embodiments, the platform frame 911 supports a platform that is lifted using belts. This way, an object could be picked up using the platform and transported anywhere along the travel path. Alternatively, the platform frame 911 may not include a platform, but rather the lift belts would directly engage an object to be transported, such as a wheelchair or gurney within a hospital.

FIG. 37 illustrates another alternative embodiment of a platform lift system having an expandable frame assembly. The expandable frame assembly enables the lift platform of the present invention to be modified to accommodate any size load. The frame assembly includes a frame formed from tubular sections 1068, 1067, 1069, and 1070. The tubular sections are telescoping such that end sections 1070 are movable within vertical sections 1068 to change the length dimension of the frame, and sections 1067 are movable over horizontal sections 1068, 1069 to change the width dimension of the frame. Locking screws 1074 rigidly fix the sections in place after a desired frame shape is selected. The frame assembly carries a sling 1073 that is connected to the frame using quick-disconnect latches 1072.. The entire frame assembly may be raised or lowered using a platform lift system as described in the previous embodiments.

FIG. 38 illustrates another alternative embodiment of a platform lift system used in connection with an overhead rail. Transverse frame tracks 1075 are suspended from a ceiling 1162 of an interior structure, such as a garage. A movable track segment 1059 extends between the transverse frame tracks 1075 and is movable along the transverse frame tracks using rollers. A platform lift system is movable on the movable track segment 1059 such that the platform lift system could be moved to any position within a space bounded by the transverse frame tracks 1075. The platform lift system could lift any sized object, such as using the expandable frame assembly of FIG. 37.

FIGS. 39 through 41 illustrate an alternative embodiment of the drop down storage system of FIGS. 12 and 13 used to lift a compartment 1060.. The compartment 1060 may include a hingedly attached gate 1078. The compartment 1060 may be suitable to transport a wheelchair.

Having thus described a preferred embodiment of a platform lift system, it should be apparent to those skilled in the art that certain advantages of the described system have been achieved. It should also be appreciated that various modifications, adaptations, and alternative embodiments thereof may be made within the scope and spirit of the present invention. 

1. A platform lift apparatus, comprising: a frame having internal and external mounting surfaces; a drive mechanism substantially disposed within said frame and coupled to said internal mounting surfaces, said drive mechanism including a plurality of rotatable, parallel shafts with each shaft further including at least one lift drum having an associated lift tether at least partially wound thereon and having an end hanging therefrom; and a platform coupled to each said lift tether end and being the thereby suspended from said frame, said platform being selectively movable by operation of said drive mechanism within in a vertical dimension between raised and lowered positions. 